1. Field of the Invention
The present invention relates to an electron beam apparatus using an electron beam and a sample observation method using the same.
2. Description of the Related Arts
“Inspection Technique”
Inspection apparatuses are conventionally used to inspect defects of semiconductor wafers. A known inspection apparatus is equipped with a primary optical system that irradiates an electron beam onto a semiconductor wafer and a secondary optical system that detects secondary electrons or reflected electrons emitted from the semiconductor wafer and generates image data from a detection signal thereof.
Wafer inspection apparatuses using electron beams are known to apply a processing method called “predosing” or “precharging” that irradiates, when observing a semiconductor wafer, charged particles onto the semiconductor wafer before the observation so that the wafer surface is charged uniformly. This kind of technique is disclosed in International Publication WO 2002/001596.
In order to perform predosing or precharging processing, a precharging unit is provided adjacent to a barrel which is an electron beam source and the precharging unit irradiates the semiconductor wafer with charged particles before observing the wafer through irradiation of an electron beam. This eliminates variations in charge, makes the charged state of the semiconductor wafer surface uniform and can thereby obtain a uniform image with less image variations.
However, according to the configuration described in aforementioned International Publication WO 2002/001596, the irradiation area where charged particles are irradiated from the precharging unit is set to be by far wider than the field of view which is the detection area of a detector of the secondary optical system. Since the irradiation area of precharging is wide, the area outside the observed portion is also charged up. Repeating precharging may destroy elements on the wafer.
Furthermore, although an optimum amount of precharging varies depending on a wiring material and insulating material of the wafer, the amount of dosing of charged particles irradiated from the precharging unit cannot be controlled precisely.
Furthermore, since the precharging unit is provided in addition to the barrel which is the electron beam source, replacement of the electron source is complicated. Furthermore, since wafer inspection using an electron beam is carried out in a vacuum atmosphere, it is necessary to additionally perform vacuuming of the space where the precharging unit is installed.
“Removal of Foreign Matter”
The present invention relates to a method of eliminating foreign matter on a sample surface and a charged particle beam apparatus used for this method, and more particularly, to a method of eliminating foreign matter on the sample surface by means of electrostatic adsorption using charging of foreign matter and a charged particle beam apparatus used for this method.
Surface inspection apparatuses are conventionally used to detect foreign matter from a wafer or the like. A known surface inspection apparatus irradiates a laser beam onto a substrate surface such as a wafer, detects scattered reflected light of the laser beam and detects foreign matter. Such a surface inspection apparatus is disclosed, for example, in Japanese Patent Laid-Open No. 2003-166947.
However, the surface inspection apparatus described in Japanese Patent Laid-Open No. 2003-166947 can detect foreign matter, yet gives no consideration to removal of the foreign matter after detection of the foreign matter. Even if the surface inspection apparatus detects foreign matter, a substrate where the foreign matter is detected cannot be shipped as is unless the detected foreign matter is removed. Thus causes yield to degrade.